Duplex circuit.



L. ESPENSCHIED.

' DUPLEX CIRCUIT.

APPLICATION FILED ocT, 13.1915.

1,5233% Patented. July 17, 1911' Myemlor: L/oya figOensch/e d;

w/mawm m' naling circuits,

NEW YORK, ASSIGNOR T AMERICAN TELEPHONE AND TELEGRAPH COMPANY, A CORPORATION OF NEW YORK.

DUPLEX CIRCUIT.

Specification of Letters Patent.

Application filed October 13, 1915. Serial No. 55,714. at

- two physical telephone circuits together fur point where the effect is sought, the phan-' him fects such as u r n .prove transmissiomreducing reflectlon losses nishing a phantom circuit, inductance of are sought in loading to 1mand conductively separating line sections by means of repeating coils, a separate inductance devicehas been employed in each of the circuits at every by autotransformers tom devices bein independent of those in the physical or side circuits. Since the side circuit current must traverse the windings of the phantom devices, it is subjected to re sistance and other losses. Thepresent invention avoids this by utilizing the effects in the devices in one class of circuits, as the sides, to roduce like effects inthe other class, as t e phantom. Considering as one of the most vention its use for loading duplex telephone circuits, it may be said that the standard toroidal lgading coil is so designed, as. to core form and winding disposition, that the windings neutralize one anothers inductance for current peculiar to the circuit which they are not intended to load, and in which they are connected mutually opposing, and the devices in diiferent circuits are also so related and with interposed media of such a character that the mutual inductances between them are negligible. In carrying outmy invention, however, the windings belonging to each circuit'are so loosely coupled inductively that this neutralization is but partial and the windings for different circuits are more closely coupled. There- 'ore inductance is introduced into both classes of circuits. invention consists in means for varying the inductance effect of the device upon one or more of the circuits to enable the ratio of the inductance in the two classes of circuits to be controlled.

In. the accompanying drawing, in which similar reference characters designate like parts throughout, Figure 1 illustrates diagrammatically one embodiment of the inproviding auxiliary structure for loading both the valuable applications of the inrated from one another by 90.

rent in the conductors Another feature of the Patented July 11?, rear.

vention applied to the loading of both physical and phantom circuits; Figs. 2 and 3 represent respectively the flux produced in the core of Fig. l by side circuit current and phantom circuit current; Fig. 4 shows another manner of disposing the line windings; Fig. 5 represents another form of the invention, in which the magnetic core is omitted; and Fig. 6 is similar to. Fig. l, with inductance ratio modifying windings added.

Referring to Fig. 1 of the drawing, the pairs of onductors A, B and C, D, represent portions of two telephone circuits in which flow talking currents, the direction of which is lndicated by the full and dashed arrows, i these physical or side circuits being combined in any convenient manner to furnish a third or phantom circuit traversed by talking current indicated by the dotted arrows. I have, in this instance, shown a unitary side and phantom circuits. This comprises a corev of magnetic material. having portions or; quad rants 10, 11, 12 and 13, equal in dimensions, arranged in the form of a symmetrical closed figure, this being illustrated as though it may obviously be of other contour. At the junctions of the portions 10, ll; and 13, which are preferably integral with one another, there-are connected other portions 10, 11", 12 and 13, also preferably integral, which appear as radial arms sepain them; ganization of Fig.1 the arms of the may be considered as the primary cor. p tions, carrying line windings L, L, if and L belonging respectively to the con-- ductors A, B, C and D. These windings are preferably so connected that the'inductaiu'res Of the windings L and L are inuti'aally aiding. for the side circuit current in conductors A and B and the windings it and J similarly related for the side circuit cur- C and D. Moreover, the pairs of windings L, L and L. L are mutuaily aiding for phantom circuit current. The relations between the induw tances may be represented by the following simple equations:

Where L ztotal side circuit inductance;

'a toroid,

' mutual inductance M 'of different side circuits,

effective toload the tance M side circuit acts against the self inductance L of the'windings and because of the close coupling is practically asgreat, and the between the windings the self inductance, is negligible because of the construction and relation of the coils. In my invention the inductance 2N is made phantom by increasing the closeness of the coupling'with respect to the windings of the coils of different side circuits, while at the same time the negative loading effect of the mutual inductance M- is reduced by decreasing the closeness of the coupling between windings of the coils 'Fig. 2 by full of the same side circuit. This is accomplished by placing the windings L, L and L for the same side circuit upon independent members of a core structure which is unitary for both side circuits, as the cross-shaped arms 10' 11 and 12, 13,

and by providing the co e withbranches 10, 11,- 12 and 13 so arranged that the flux originating in any winding, is not confined to its companion winding, but is diverted in part through the windings belonging to the other side circuit. This will best be and 3 of understood by reference to Figs. 2

For any instantaneous ourthe drawings. rent peculiar to the side circuits, or flowing serially in each, the flux due to the windings L L and L, L is representedin and dashed arrows, respectively. It should be noted that the fiuX due to the windings of one side circuit does not link with the windings of the other, so that the side circuits are non-interfering. In ,Fig. 3 is represented-in dotted lines the flux resulting from the phantom current, which passes serially through bothside circuits with the windings of each in parallel. Here, for example, the flux leaving primary portions 10 and 11 of the core divides, .fiowing'in opposite'directions through the secondary portions 10, 18 and 11, 12, respectively, and there unites and completes its circuit through the primary core portions 13 and 12'. This linkage of flux between the windingsof different side circuits gives which would aid side circuit current.

- any suitable effective mutual inductance in the side circuit pair d'ue to the two effects thus "neutralize. one another, and the phantom'and side circuits are therefore mutually non-inter ring;

Insteadaof placing the line windings upon thearm portions of the core they may be disposed upon the outer portions 10, 11, 12 and 13,- as is illustrated in Fig. 4. But since, as appears from Figs. 2 and 3, the flux in the arms divides into two'components extending in opposite directions about the toroid, it is necessary to employ two turns of winding upon the outer, or what is now the primary, portion for each turn used in the arrangement of Fig. 1 to obtain the same result. ductor are therefore arranged in two sections L105. L101); Lila, Lin Liza Lrzb; d L L located respectively upon adjacent toroid quadrants with the windings of one side circuit staggered 90 with respect to the windings of the other side circuit. The two winding sections on each quadrant are preferably wound one above the other, one of the sections of each winding occupying an inner position on one quadrant and the other an outer position on the adjacent quadrant. The two' sections for each con ductor are connected mutually opposing, and the two sections for companion conductors, which are on adjacent core quadrants, are connected mutually aiding for The two superposed sections on each quadrant are connected mutually aiding for phantom current. The

flux distribution and ratio of phantom to side circuit inductance are as in the organization of Fig. 1.

The generic conception of this invention does not require that a core of magnetic material be employed. The core structure may be what is termed the air-core type, which is such an arrangement as illustrated in Fig. 5. The line windings L L, L" and L appearmounted upon the arms of a cross-shaped frame F which may be of non-magnetic material as wood. The relations between the windings and the flux created may be as is illustrated -in Figs. 1 to 3; and though the magnetic coupling between the windings will, of course, be less, by suitably proportioning the windings'the desired loading action may be obtained.

The mutual inductances which affect the electromagnetic balance between circuits are those between line windings of different side circuits. In order that the component circuits be balanced, and hence no'n-intferfering in this respect, it is necessary that there be no resultant mutual inductance bet f een the three circuits; that is, thatthe'four ut'ual inductances between the four line windingsneutralize ,one another. To provide that'the between the cir- The windings of each conaser/cc cuits be zero, two of the. four mutual.inductances must balance the other two. In

the arrangements described, the windings of one side'circuit are symmetrically disposed poled that two act other two for either the side circuit connection in bothside circuits circuit and phantom circuit will be theoretically (thecondition for zero side-to-sidecrosstalk) or for the side circuit connection in one circuit and the phantom circuit connection'in the other circuit (the condition for l zero phantom-to-side crosstalk). All are therefore theoretically balanced as to mutual inductances' Theyare also, by symmetry of design, balanced electrostatically and with respect to efiective resistance and self inductance. In consequence of this, there no crosstalk between the several circuits of the loading unit.

In loading phantom and side circuits a ratio of 10.6 between the respective inductances is often desired, while none of the plans hereinbefore described will give a higher ratio than 0.5. To enable this ratio to be so controlled that the proper relation may be established, 1 provide auxiliary means-for varying. either. or both the side inductances'. As illustrated in Fig. 6, this means takes the form of auxiliary windings 2'', Z", Z and Z. In the present instance it is assumed that the ratio of the phantoni' to the side circuit inductance is to be increased. In such case, I

s may b'eupon it is preferablethough the auxiliary windin either of the core portions, to place them upon arms 10, 11, 12 and 13 of the core which are traversed by all the flux due to the phan torn' circuit. This requires but half as many turns of auxiliary windings as would be the case were they upon the portions 10, 11, 19; and 13, in which the phantom flux is divided (see Figs. 2 and Considering any one ofthe four line conductors, as A, it is connected to the outer terminal of the main winding L upon the arm 10' of the core, with the inner extremity of this winding end of the auxiliary winding 1, situated upon tlie arm 11- of the core and being Wound in the opposite direction to L. The line conductor A continues from the outer terminal of the winding Z Line conductorsB, C and D are similarly joined to the main windings L, L and L upon the core arms 11, 12 and 13, respectively, and to the auxiliary windings Z Z and Z upon the core arms 10, 13 and 12, respectively. The auxiliary windings when thus located are placed over the primary windings and are closely coupled therewith inductively,

so as to cause a maximumdiilerence in their net inductance for the phantom and side circuit currents. The auxlliary windings are connected in such a mannerthat their inducportions and joined to the inner tances act simultaneously to decrease the side circuit inductance and to increase the phantom circuit inductance, the ratio sought being obtained by altering thenumber of turns ofthese modifying windings.

Each auxiliary winding may be applied to the core member in two sections, so arranged that the relation between the sections causes the inductances for one class of current, say in the side circuits, to neutralize one another, while for the other circuit, as the phantom, the inductances are added to each other and those of the primary windings. Here, however, one of the. sections may be, in eflect, merely a continuation of the corresponding primary windings'and is most conveniently provided by increasing the number of turns of the latter. 'This ar-- rangement is therefore not trated.

The division of separately illusline windings, of a separate sections and sections upon the associated trated for example in Fig. 4 of the drawings, is not claimed herein, but relates to a different invention claimed'in my copending application Serial No. 55,716, filed October 13, 1915, renewed June 14:, l9l7,Serial No. 174,778.' Other specific embodiments of the invention herein claimed are disclosed in my copending applications Serial Nos. 55,715, 55.716 (renewal Sr. No. 174,778) and 55,717, filed October. 13th, 1915. v

I claim: p 1. The combination with two physical circuits consisting of line conductors together furnishing aphantom circuit, of an inductance' device comprising a magnetic core having primary connected portions-and secondary connected portions connected thereto, there being line windings upon the primary the secondary portions furmshing continuous return paths-for flux from the primary portions.

2. The combination of two physical circuits consisting of line conductors together furnishing a phantom circuit, of an induc tance device comprising a magnetic core having primary connected portions and secondary connected portions connected thereto, there being line windings confined to the primary portions and the secondary portions furnishing continuous return paths for flux from the primary portions.

3. The combination of two physical circuits consisting of line conductors together core, as illusfurnishinga phantom circuit, of an induc- The combination of two physical circuits consisting of line conductors together furnishing a phantom circuit, of an inductance device comprising a magnetic core havi ing aplurality of portions connected to form, a closed figure, another set of core portions;

from the junctions of the first-named por-' tions, and a winding upon each of the second-named core portions and being included in the conductors of: the duplex circuit.

' cuits consisting of line conductors together furnishing aphantom circuit, of a loading.

a core portion of toroidal coil comprising of other core portions ]01I1- 'form, a plurality ing opposite sides of the toroid, and a windin in each line conductor, said windings being upon said other core portions.

7. The combination cuits consisting of line conductors together 80 furnishing a phantom circuit, of an inductance device comprising. a core portion of toroidal form and portions joining opposite sides of the toroid, and a winding for each line conductor, said windings beingsituated 55 upon the core portions separated by 90 from one another. v 8. The combination of two physical circuits consisting of line conductors together furnishing a phantom circuit, of an induc- 40 tance device comprising a core portion of toroidal fOrm and radial portions situated from one another and joining opposite .sides of the toroid, and a winding for each line conductor, said windings being, situated on said radial portions. I

9, The combination with two physical circuits consisting of line conductors together iu'rnishing a phantom circuit, of windings included-1n the conductors of each 'hysical, $0 circuit in oppositely disposed pairs, t e' pairs of windings in the same physical circuit being connected to produce loadin 1e ,ects

therein and the windin pairs being 7 closely con produce loading efiectsiin cuit;- l I 10.:Te combination with two physical circuits.v consistingv of line conductors gether furnishing-- a phantom circuit,

the phantom cir-' winding included in the conductors of each physica circuit in-oppositelyi disposed pairs,

the windings belongingtoeachaphysical cirg coupled andthe windings belonging tolli' erent circuits being closely coupled, said windings producing inductance having four connected 1'5 portions and other core portions extending 6. The combination of two physical cir with two physical cir physical circuit v {effects in the physical circuits and also pro- .fd ici'ng inductance effects in the phantom l circiiit.

11. The combiriation with two physical circuits consisting of line conductors together furnishing a phantom circuit, of

windings included in the conductors of each a physical circuit in oppositely disposed pairs,

physical cirthe windings belonging to each cuit being loosely coupled and b'elonging to different circuits cbupled, the windings of the circuit pairs being'separated by 90 said windingsbeing adapted to produce in ductance effects in the physical circuits and also to produce inductance effects. in the phantom circuit.

12. Thecombination with two physical circuits consisting of line conductors togethenfurnishing a phantom circuit, of an inductance device comprising a magnetic core having opposite primary connecting portions, and a winding for each line conductor, the windings of the conductors of the two lines being respectively situated in pairs upon opposite pairs of primary core portions.

13. The combination with two physical the windings portions and being closely from one another,

circuits consisting of line conductors together furnishing a phantom circuit, of an inductance device comprising a magnetic core having opposite primary portions and connecting portions, and a winding for each line conductor,the windings of the conductors of the two ated in'pairs upon opposite pairs of primary core portions and the pairs of windings being separated b 90 from one another.

14. The com ination with two physical circuits consisting of line conductors tolines being respectively situ 1 ill v15. The combinationv with two physical circuits. consisting of line conductors to gether furnishing a phantom circuit, of windings included in the conductors of each in oppositely disposed pairs, the windin sbelo iging to each physical circuit being loosely coupled and the windings belonging to difierent circuit-s being closely coupled, said windings producing inductance vcfi'ects in the-physical circuits and also pro- .ducing inductance efi'ects in the phantom circuit, and means cooperating with said in- 'diictance means for varying the loading effect uponone of said circuits,

messes members being associated to produce still another inductance effect, and auxiliary windings for partially neutralizing the last named inductance ei'iiect.

18. In a duplex circuit, the combination with windings for producing a loading ctfect, said windings being associated to pro duce another distinct loadingeffect, of anti-- iliary windings associated with-those first named and adapted to'partially neutralize one of said loading eii'eots to modify the relation of such"loadingeiiects.

19. An inductance device comprising a core having a plurality of portions, other core portions connecting those first nanied, inductance windings upon one set of cpre portions, and inductance controlling wind ings upon the core portions.

20. An inductance device comprising a core having a plurality of portions, other core portions connecting those first-named,

inductance windings upon one set of core portions, and inductance controlling windings upon the same set of core portions.

21. A duplex circuit consisting, of two physical circuits and a phantom circuit furnished thereby, of a plurality of primary inductance windings for loading a circuit, said windings being associated with one another to also load another of the circuits, and auxiliary windings associated with the primary inductance 'windings to modify their loading efiect.

22. A duplex telephone circuit consisting of two physicalcircuits and a phantom fur nished thereby, a plurality of inductance members adapted to load the physical circuits, said members being inductively related to one another whereby the phantom circuit is also loaded, andinductance controlling windings associated with the members for phantom.

23. A. loadingcoil comprising a core portion of toroidal vform, a plurality of other core portions joining the sides of the toroid, primary inductance windings upon said other core portions, and/auxiliary induetance windings located outside the primary windings.

in testimony whereof, l have signed my name to this specification in the resence of two subscribing witnesses, this 22th day of September, 1915. V. LLOYD ESPENSCHIED. i lfitnesses (Inns. G. Harem, J r., A. C. Fnanca.

modifying 'their loading effect upon the 

